The present invention relates to improvements in a clutch comprising a drive rotary member, a driven rotary member engageable with and disengageable from the drive rotary member by being moved relative thereto in the directions of axis of rotation, the driven rotary member being biased toward the drive rotary member for engagement therewith, an annular cam interposed between the drive rotary member and the driven rotary member and rotatable about the axis of rotation, and an engaging member manually operable mounted on a case to prevent rotation of the cam, the driven rotary member and the cam being formed in facing relation to each other with wave-shaped cam surfaces respectively, the driven rotary member and the cam being rotatable relative to each other to permit the cam surfaces to ride on each other, whereby the driven rotary member is forced away from the drive rotary member.
The clutch of the type described has the feature of being smoothly and accurately engageable and disengageable as desired by a small force which is derived from the torque of the drive rotary member to operate the engaging member alone. However, since the wave-shaped cam surfaces are used to displace the driven rotary member, the clutch is liable to produce noises and vibrations when disengaged.
More specifically, the wave-shaped cam surfaces formed in face-to-face relation on the cam and the driven rotary member respectively are so adapted that the crest portions of the cam contact each other when the driven rotary member is forced away from the drive rotary member in the direction of axis of rotation. Accordingly the crest portions tend to be out of contact, permitting repeated engagement of the wave-shaped cam surfaces due to the overrun of the driven rotary member and consequently producing noises and vibrations. This invention intends to overcome these problems.